The present invention relates generally to scroll compressors and more specifically to scroll compressors incorporating capacity modulation systems of the delayed suction type.
A wide variety of systems have been developed in order to accomplish capacity modulation most of which delay the point at which compression of the fluid in the moving fluid pockets begins. In one form, such systems commonly employ a pair of vent passages communicating between suction pressure and the outermost pair of moving fluid pockets. Typically these passages open into the moving fluid pockets at a position normally within 360.degree. of the sealing point of the outer ends of the wraps. Some systems employ separate solenoid valves for each such vent passage which valves are intended to be operated simultaneously so as to ensure a pressure balance between the two fluid pockets. Other systems employ additional passages to place the two vent passages in fluid communication thereby enabling use of a single valve to control capacity modulation.
More recently a capacity modulation system of the delayed suction type for scroll compressors has been developed in which a valving ring is movably supported on the non-orbiting scroll member. An actuating piston is provided which operates to rotate the valving ring relative to the non-orbiting scroll member to thereby selectively open and close one or more vent passages which communicate with selective ones of the moving fluid pockets to thereby vent the pockets to suction. A scroll-type compressor incorporating this type of capacity modulation system is disclosed in U.S. Pat. No. 5,678,985 the disclosure of which is hereby incorporated by reference.
While this system provides an extremely efficient means by which to modulate the capacity of scroll compressors, the need to minimize or prevent leakage past the valving ring when the compressor is in a full capacity operating mode requires tight manufacturing tolerances between the interfitting ring and scroll surfaces. If the clearances are too tight, it is possible that the valving ring may bind whereas if the clearances are too great, there will be excessive leakage. Further, maintaining such tight tolerances results in increased manufacturing costs. Of course, if the clearances are relaxed, the increased leakage resulting will reduce the efficiency of the compressor.
The present invention overcomes these disadvantages by incorporating individual seals associated with the valving ring which are designed to effectively prevent fluid leakage from the vent passages when the compressor is in a fill load operating mode. By utilizing such seals, the manufacturing tolerances between the valving ring and scroll member may be relaxed thereby reducing the manufacturing costs while still maintaining the desired high level of operating efficiency. In one form the seals are mounted on and movable with the valving ring. In another embodiment, the seals are mounted on the non-orbiting scroll in surrounding relationship to the vent passages provided therein. Preferably the seals will be structured such that the fluid pressure from the vent passages will act to bias the seals into sealing engagement with the opposed surface. Alternatively, a biasing spring may be utilized to aid in biasing the seal. Additionally, a localized flat may be provided on the facing surface against which the seals seat to further facilitate sealing engagement therebetween.
Additional advantages and features of the present invention will become apparent from the subsequent description and the appended claims taken in conjunction with the accompanying drawings.